15x-10-14x-7=12x-20
15x-14x-12x=-20+10+7
-11x=-3
x=3/11
13x-9x-x=8+21-5. 3x=24. X=8
Берем производную
<span>y' = 36/(cos(x))^2-36 = 0 </span>
<span>cos(x)=1 x=2*pi*n </span>
<span>cos(x)=-1 x=pi+2pi*n </span>
<span>x лежит [-pi/4; pi/4] => x=0 </span>
<span>y(-pi/4) =18*pi -40 наименьшее </span>
<span>y(pi/4) = 32 наибольшее </span>
<span>y(0) = 9pi-4</span>